Even I have the video converted to MP4 format using Sothink Video Converter and was able to drag and drop it in iTune. But when i try to sync it with the phone nothing happens and iTunes says "There are no rented movies in your iTunes library that can be transferred". what to do?

Try Importing to itunes instead of drag/drop sometimes this affects the compression to itunes. Also attempt playing the video on your computer first because there is a possibly that the converter didn't do its job.
Post back w/results please

Try Importing to itunes instead of drag/drop sometimes this affects the compression to itunes. Also attempt playing the video on your computer first because there is a possibly that the converter didn't do its job.
Post back w/results please

Thanks for the reply.

I am not getting any option to import the video. I am albe to import only the music files into itunes. And yes, after drag/drop, I played the video in itunes and it worked fine.

Only thing here is, when i do sync, it says, sync completed. OK to disconnect. but the video file is not getting synced to iPhone.

Just download ifunbox from google and connect your iphone to your system,then open ifunbox and you can transfer almost anything to your iphone,you can also use transmanager which helps you to copy only songs and videos to your iphone